The detection of keratoconus is a major concern in the screening of refractive surgical patients, since it is known that its presence weakens the corneal stroma and can lead to iatrogenic ectasia. While clinical keratoconus is reliably detected with corneal topography and slit-lamp examination, means to detect the possibility of keratoconus in its earliest stages prior to the presence of slit-lamp findings have been extensively explored, and it is generally agreed that the first detectable sign of keratoconus is a localised steepening seen with Placido corneal topography. Several terms have been put forward to describe this condition including preclinical keratoconus, keratoconus suspect and forme fruste keratoconus. While these designations have been used interchangeably, doing so has led to problems in understanding the natural history of keratoconus.

Despite this short-coming, excellent longitudinal studies are being conducted and are slowly emerging in the literature. In the June issue, Shirayama-Suzuki and colleagues1 examined keratoconus progression in the fellow eye in unilateral keratoconus patients over the course of 6 years. The fellow eyes were included if they had no slit-lamp signs of keratoconus or deterioration of spectacle-corrected visual acuity. The authors found that just over 20% of the fellow eyes progressed to clinical keratoconus with evidence of increased asymmetry, spherical equivalent and higher-order irregularities, which they documented with topographic indices and Fourier analysis. As they note, keratoconus is a slowly progressing disease, and therefore it is likely that a longer follow-up would result in more of their cohort progressing to clinical keratoconus.

This study provides a …